Due date and pregnancy week calculator

It calculates your estimated due date and how many weeks pregnant you are today. The calculation follows Committee Opinion No. 700 of the American College of Obstetricians and Gynecologists (ACOG): the due date is 280 days after the first day of the last menstrual period. The conception, IVF transfer and ultrasound methods are derived from the same rule. The result shows the estimated date, your weeks and days today, your trimester, the days left and the normal 37–42 week window for birth. When signed in you can save the date to your account and follow your week in the parent dashboard.

First choose the method that matches the date you know. If you know your last period, enter the day it started and choose your cycle length; if your cycle is shorter or longer than 28 days, the date shifts by the difference. If you know the day you conceived or ovulated, enter that day. For IVF, enter the transfer day and choose whether the embryo was 3 or 5 days old. If you have had an ultrasound, enter the scan date and the gestational age written in the report. The result updates as you type.

Pregnancy weeks are counted from the first day of the last period, so conception falls around week 2. “24 weeks 3 days” means 24 full weeks are complete and you are on day 3 of week 25. The due date is a target, not a fixed day: a pregnancy normally lasts between 37 and 42 weeks. Trimesters: first trimester weeks 0–13, second trimester weeks 14–27, third trimester from week 28 until birth.

This is an estimate. According to ACOG, a first-trimester ultrasound is the most accurate way to date a pregnancy; if the ultrasound date differs from the one based on your last period, the date set by your doctor or midwife applies. With an irregular cycle, a calculation based on the last period is less reliable. The tool does not predict the baby's sex; lunar calendars and similar methods are not scientific, and the tool does not use them.